Day 22 Motors & Magnetic Fields

At the beginning of the class, we drew the microscopic level different between ordinary pin and the magnetic pin. The magnetic pin is in order, and ordinary pin is not in order.

We listed two ways to destroy a magnet, which are heating and hitting because they can cause vibration that reorganize the domains.

The professor demonstrated the activity by heating the pin. The result was it lost its magnetic.

This picture shows another exercise where we give the loop a magnet field, the direction is upward. We found that only the top and the bottom have force and they cancel with each other. We also found F = BIL and τ = 1/2 BIL^2 

We did a problem by using the question highlight in yellow.

Professor showed us an electric motor 

There are three ways that a motor would break, the brushes, the commutator, and the coil contact foils.

Then we started doing an experiment called electric motor. We need to set up the apparatus like in the diagram.

There are four situations of the motion of electric motor. We found that when the direction of the current change or direction of magnetic field change, the direction of rotation will also change.

These are the answers from lab manual.

Then we performed another experiment about making a simple electric motor by coated wire, two paper clip, a bar of magnet

This video shows how the experiment is successfully done~

In the picture shows the hall effect and hall voltage Vh = B*I/p*q*t

The next activity is giving the bar in the magnetic field and observing how the compass arrow will turn

We predict that the compass would point like a circle.

In this picture, the result and our prediction match.

This picture shows the change in opposite current also make the compass circle circle point the opposite direction. 

In this activity, the professor let us draw where the compass will point in such wiring arrangement. And our prediction is on the right.

We found B as u_o*q*dv*r/4π*r^2

We also found the relationship between Force of Magnetic field and force of the electric field.

Conclusion

In today's class, we first discussed about the magnet, then we talked about the force and torque related to magnetic field. Then we also talked about magnetic dipole moment. We also looked at the electric motor and built a simple electric motor. Then we also learned the hall effect and Biot-Savart Law. Finally we figured out the relationship between  force of magnetic field and force of the electric field